Advantage

It's easy to change the models! Place the model on the map for any hero, open the map properties tree, select the hero, and in the map properties tree, you should see, next to the "shared" window: "AdvMapHeroShared." Then, depending on the hero, click on all of this. There will be the following options: ... to edit and choose a different hero, "new" - to create a new hero (when I create a new hero, the editor gives me an error). Then, a window will open, and it will look like this:
Model Model:_(Model)\Creatures\Haven\Paladin_LOD.(Model) - model
AnimSet AnimSet:Characters\Creatures\Renegades\Champion-adv - animation set

blockedTiles
holeTiles
activeTiles
activeTiles.[0]
activeTiles.[0].x 0
activeTiles.[0].y 0
passableTiles
PossessionMarkerTile
PossessionMarkerTile.x 0
PossessionMarkerTile.y 0
Effect null - effect
EffectWhenOwned null
messagesFileRef
WaterBased false
ApplyHeroTrace false
SoundEffect null - sound for interaction of the hero with an object
flybyMessageFileRef
ObjectTypeFileRef Text/Visibility_Types/Units.txt
TerrainAligned false
FlyPassable true
AdventureSoundEffect null - sound for playing on the adventure map; if AnimSet exists, the sound is taken from the current animation
RazedStatic null
Icon128 null - icon
InternalName Dalom - script name
Class HERO_CLASS_KNIGHT - hero class
Specialization HERO_SPEC_POISONER - specialization
PrimarySkill - skill
PrimarySkill.Mastery MASTERY_BASIC - skill level
PrimarySkill.SkillID HERO_SKILL_TRAINING - skill class
SpecializationNameFileRef Text/Game/Heroes/Specializations/Dungeon/Poisoner/Name.txt
SpecializationDescFileRef Text/Game/Heroes/Specializations/Dungeon/Poisoner/Description.txt
SpecializationIconTexture:Textures\HeroScreen\Specializations\Dungeon\Poisoner - specialization icon
FaceTexture Texture:Textures\Icons\Heroes\Heaven\Heaven_Klaus_128x128.(Texture) - character photo
FaceTextureSmall Texture:Textures\Icons\Heroes\Heaven\Heaven_Klaus_128x128_64.(Texture) - photo in the town
HeroCharacterArena Character:Characters\Creatures\Haven\Paladin_LOD.(Character) - model in the arena
HeroCharacterArenaMelee null - hero model for melee attack
HeroCharacterAdventure Character:Characters\Creatures\Haven\Paladin_LOD.(Character) - hero view on the map
HeroIndividualCamera null - camera for this hero for the hero screen
CombatVisual CreatureVisual:GameMechanics\CreatureVisual\Creatures\Haven\Paladin
TownType TOWN_DUNGEON - town type
Editable
Editable.NameFileRef Text/Game/Heroes/Persons/Dungeon/Dalom/Name.txt
Editable.BiographyFileRef Text/Game/Heroes/Persons/Dungeon/Dalom/Bio.txt
Editable.Offence 1
Editable.Defence 0
Editable.Spellpower 3
Editable.Knowledge 1
Editable.skills
Editable.skills.[0]
Editable.skills.[0].Mastery MASTERY_BASIC
Editable.skills.[0].SkillID HERO_SKILL_DARK_MAGIC
Editable.perkIDs
Editable.spellIDs
Editable.spellIDs.[0] SPELL_PLAGUE
Editable.Ballista false
Editable.FirstAidTent false
Editable.AmmoCart false
Editable.FavoriteEnemies
Editable.TalismanLevel 0
ArrowButtonState 0
Decal null
Selection Model:_(Model)\Heroes\Warlock_Path\Symbol
Trace AdvMapHeroTraceSet:MapObjects\_(AdvMapHeroTraceSet)\Dungeon
RaceTraitIcon null
RaceTraitDescFileRef
ScenarioHero false
AdventureMusic null - adventure music
HideInEditor false
PresetMinimalAttributes
PresetMinimalAttributes.Offence 2
PresetMinimalAttributes.Defence 2
PresetMinimalAttributes.Spellpower 2
PresetMinimalAttributes.Knowledge 2

Added 2 minutes ago
I apologize for everything; I just did it quickly in 3 hours. I can't replace Necromancers with Demons; I have a series of maps about these characters. Do you want me to upload it specifically for you?